1. Field of the Invention
This invention relates to a pharmaceutically active plant extract and composition thereof. More particularly, this invention is concerned with a process for preparing a substantially alkaloid-free aqueous or dry extract from an aconite root, i.e., a root of Aconitum japonicum Thunberg or any other like-plant belonging to the genus Aconitum, the family Ranunculaceae, and pharmaceutical preparations containing such an extract.
2. Description of the Prior Art
An aconite root is the root of Aconitum plant such as Aconitum japonicum Thunberg or Aconitum sinense Siebold, and is listed in e.g. the 7th Revision of the Japanese Pharmacopoeia. It has long been known that the aconite root is useful as a cardiotonic, analgesic or antiphlogistic, and is also effective for retarding ageing and invigoration by promoting the metabolism. A crude drug prepared from it is used internally in the form of powder or a decoction, and on rare occasions, the crude drug in powder form is applied externally for relieving neuralgia and rheumatism. As is obvious from the fact that the Ainu race applies it to the arrows when hunting bears, this crude drug is highly poisonous, and can often cause anesthesia leading to death if used in a wrong quantity. The toxicity of the drug is due to a dozen or so alkaloids contained in the aconite root, such as aconitine (C.sub.34 H.sub.47 O.sub.11 N), mesaconitine (C.sub.33 H.sub.45 O.sub.11 N), hypaconitine (C.sub.33 H.sub.45 O.sub.10 N) and atisine (C.sub.22 H.sub.33 O.sub.2 N). Aconitine is present in a greater quantity than any other alkaloid, and is so toxic that a man will die if he takes 3 or 4 mg of aconitine. The cardiotonic, analgesic and antiphlogistic actions of the aconite root have hitherto been attributed to its alkaloids, particularly aconitine or like alkaloids, and those formed by removing acetyl and benzoyl groups from aconitine or like alkaloids [Jiro Imai: Journal of Tokyo Medical College, 7, 1 (1949), Teijiro Agawa: Journal of Tokyo Medical College, 12, 1 (1954), and Hirohisa Goto: Journal of Jap. Soc. of Pharmacology, 52, 4 (1956)]. Accordingly, there have been proposed a number of methods for processing the aconite root to reduce its toxicity as far as possible. As it has been considered that the removal of the acetyl group from virulently poisonous aconitine converts it to benzoylaconine having a relatively low toxicity, one of those methods provides a processed aconite root prepared by heating an aconite root under pressure to convert the greater part of its aconitine into benzoylaconite (Japanese Pat. No. 406,780). Another method provides a steamed aconite root prepared by immersing an aconite root in bittern, and subjection it to prolonged steaming treatment to convert its aconitine into benzoylaconine. Benzoylaconine is, However, a poisonous alkaloid, as it shows a lethal dose of 27.2 mg/kg when injected hypodermically into a domestic animal, though it is certainly lower in toxicity than aconitine, which has a lethal dose of 0.131 mg/kg. Thus, the processed and steamed aconite roots are both specified as powerful drugs by the Minister of Public Welfare in Japan.